The present invention relates to an internal combustion engine connecting rod whose end is divided and disposed circumferentially with respect to a hole formed therein, and which has a slide metal piece mounted in the hole. More particularly, the invention relates to a technique for preventing relative rotation of the slide metal piece with respect to the hole.
FIG. 10A is a perspective view showing a large end of the main body of the internal combustion engine connecting rod (referred to simply as xe2x80x9cconnecting rodxe2x80x9d hereinafter) having the structure described above. A hole 2 is formed in the center of the large end 1. The large end 1 is divided into a rod portion 3 and a cap portion 4 which are disposed as two semi-circles in the longitudinal direction of the hole 2, and the rod portion 3 and the cap portion 4 are mounted with bolts which are not shown in the drawing. At an inner periphery of one mating surface vicinity of the rod portion 3 and the cap portion 4, as shown in an enlarged view in FIG. 10B, grooves 5 which are in the circumferential direction and which gradually deepen until the mating surface is reached, are formed so as to be on different sides from each other, and such that the mating surface is disposed therebetween. The slide metal piece 10 shown in FIG. 11 is mounted in the hole 2 of the connecting rod body having the structure described above.
As shown in FIG. 11A, the slide metal piece 10 comprises two ring halves 10a and 10b obtained by dividing the ring. At one mating portion of the ring halves 10a and 10b, nails 11 which extend from the outer periphery side are formed so as to be opposite to each other. The slide metal piece 10 is fit into the hole 2 by the nails 11 being accommodated in the grooves 5 of the connecting rods, and the slide metal piece is mounted into the hole 2 with a fixed tightness by tightening the bolts. Furthermore, relative movement of the slide metal piece 10 is prevented by the end surfaces of the nails 11 which are accommodated in the grooves 5, being caused to abut the end surface of the rod portion 3 or the cap portion 4.
In this invention, the rod portion 3 and the cap portion 4 are formed separately by sintering, forging, casting or the like, but they may also be formed integrally. In the case where the rod portion 3 and the cap portion 4 are formed integrally, the connecting rod may be formed first, and then the hole and the grooves are mechanically machined. The rod portion and the cap portion are then divided by being split so as to break, and thus have a similar structure to that described above, and then the slide metal piece is mounted. In this case, the machining of grooves like those shown in FIG. 10B is difficult. As a result, as shown by the broken lines in the same drawing, the connecting rod is machined to form grooves which straddle the rod portion 3 and the cap portion 4. Furthermore, for both the embodiment having the rod portion 3 and the cap portion 4 formed separately, and for that having the integral structure, which was divided by being mechanically machined and then carrying out a breaking-split, the slide metal piece may be mounted without providing grooves for fixing the slide metal piece.
FIG. 12A is a cross sectional view showing the breaking-split type connecting rod described above in a state in which the crank pin 15 is mounted. Because the nail 11 of the slide metal piece 10 does not abut the end surface inside the groove 5, as shown in FIG. 12B, the slide metal piece 10 may rotate due to deformation of the large end 1 caused by load being exerted on the connecting rod. In addition, by being deformed from the unloaded state in FIG. 13A, to the state in FIG. 13B in which the large end was deformed in the longitudinal direction thereof, as shown in FIG. 13C, the nail 11 is pressed in the direction of the arrow and there is a danger that the base plate B will eventually breaking due to fatigue. Also, broken pieces from the nail 11 may become caught between the crank pin 15 and the slide metal piece 10, and in the worst case, the slide metal piece 10 and the crank pin 15 may heat up.
In addition, as shown in FIG. 14A, a slide metal piece 10 having no nail may also be used. In this case, it is easier for the large end to deform due to load applied to the connecting rod than in the case described above in which the slide metal piece is provided with nails. As shown in FIG. 14A, crush relief portions 20 are formed at both ends of the ring halves 10a and 10b which comprise the slide metal piece 10. The crush relief portion 20 is formed such that its thickness decreases as the end thereof is approached, by causing the diameter of the inner peripheral surface to gradually increase as the end is approached. As shown in FIG. 14B, in the connecting rod in which the rod portion 3 and the cap portion 4 are separately formed, when these two portions are mounted, the joint surface may be slid. In this case, the crush relief portions 20 prevent localized contact between the slide metal piece 10 and the crank pin 15.
Furthermore, if the crush height (the height of the slide metal piece which projects from the hole in the large end in an unloaded state) is excessive, due to the elastic deformation of the mating portion of the ring halves 10a and 10b, the crush height portion distends toward the inner side, and the effective inner diameter of the shaft receiving metal piece is decreased. In that case also, the crush relief portion 20 functions to prevent localized contact between the slide metal piece 10 and the crank pin 15.
However, when the slide metal piece 10 rotates for the above described reason, the crush relief portion 20 is not able to function to prevent the localized contact between the slide metal piece 10 and the crank pin 15. That is to say, the crush relief portion 20 functions to prevent localized contact between the slide metal piece 10 and the crank pin 15 along the direction of the joint surface of the rod portion 3 and the cap portion 4. Accordingly, when as shown in FIG. 14C, the slide metal piece 10 rotates and the phase is slid, the portion which is slid and distends towards the inner side becomes close to the crank pin 15 side, and thus there is localized contact between the sliding portion and the crank pin 15. Furthermore, when the large end 1 in an unloaded state shown in FIG. 13A is deformed in the longitudinal direction so as to be in the state shown in the FIG. 13B, localized contact is more intense, and this may cause great damage to the inner peripheral surface of the slide metal piece 10.
Furthermore, this problem is common to all configurations of the slide metal piece, and due to deformation and the like of the large end caused by load being applied to the connecting rod, relative micro slippage of the slide metal piece and the hole in the large end with respect to each other is caused. Thus, fretting is generated when the outer peripheral surface of the slide metal piece and the inner peripheral surface of the hole contact. That is to say, when the large end 1 deforms in the longitudinal direction as shown in FIG. 13B, because the deformation of the hole 2 of the large end 1 of the slide metal piece 10 is not in exactly the same manner, relative micro slippage of the slide metal piece 10 and the hole 2 with respect to each other is caused. In addition wear dust, generated due to fretting, accumulates between the slide metal piece 10 and the crank pin 15, and this damages the slide surface. Also, minute cracks caused by fretting at the inner surface of the hole 2 develop, and in the worst case, there is the danger that the connecting rod will be damaged.
Thus, an object of the present invention is to provide a connecting rod in which rotation and relative slippage of the slide metal piece is restricted, and the problems described above are eliminated.
The present invention is a connecting rod comprising a hole in the end of the connecting rod main body, the end being divided into a plurality of parts which are in a circumferential direction with respect to the hole and a slide member is disposed on the inner peripheral surface of the hole, wherein the inner peripheral surface of the hole is provided with slits which extend in one direction at an angle of 13 to 90xc2x0 with respect to the circumferential direction.
In the connecting rod having the above described structure, slits are provided at a predetermined angle in a circumferential direction with respect to the inner peripheral surface of an end of the connecting rod main body. As a result, frictional resistance of the slide member is increased due to the unevenness of the slits, and relative rotation of the slide member is restricted. The slits may be formed by a polishing process such honing, grinding with a grindstone, or by carrying out shaving using a bite, or with a rotating tool such as a drill, a reamer, an end mill or the like. Furthermore, by adjusting the conveying speed and the rotation speed of the tool when the process is being carried out, the angle of the slits with respect to the circumferential direction of the hole can be set at 13 to 90xc2x0. It is to be noted that for making the angle of the slits 90xc2x0, broaching, for example, may be carried out. However, in the case of the rotation processing, if consideration is given to processability, it is preferable that the slit angle does not exceed 35xc2x0.
When the slits are to be formed, by passing the tool through the hole in one direction thereof one time, or alternatively a number of times, slits can be formed which extend in one direction (linear slitting). In the present invention, the tool such as the grindstone, the bite and the like, may also be inserted from the direction opposite to the direction referred to above to form slits which cross the slits which were first formed (cross slitting). That is to say, the present invention is a connecting rod comprising a hole in the end of the connecting rod main body, the end being divided into a plurality of parts which are in a circumferential direction with respect to the hole and a slide member is disposed on the inner peripheral surface of the hole, wherein the inner peripheral surface of the hole is provided with slits which extend in one direction at an angle of 17 to 90xc2x0 with respect to the circumferential direction and also with slits that extend in a direction which crosses the one direction. It is to be noted that, in the case of cross slitting, the slits will form a net meshing and thus there is some reduction in frictional resistance. For this reason, it is necessary to set the angle so as to be larger in the case of cross slitting than in the case of linear slitting.